{
  "$schema": "https://public-agents.com/schemas/evidence-probe.schema.json",
  "schemaVersion": 1,
  "id": "p-20260930-microsoft-learn-openai-compatible-unknown-tool",
  "subject": {
    "type": "tool",
    "id": "microsoft-learn-mcp"
  },
  "surface": "https://learn.microsoft.com/api/mcp/openai-compatible",
  "question": "access",
  "request": {
    "method": "POST",
    "credentials": "none",
    "payment": "none",
    "from": "a cloud container in a datacenter network, egress 205.188.204.187",
    "body": "one keyless tools/call of microsoft_docs_fetch on the OpenAI-compatible endpoint, with a real learn.microsoft.com article URL, jsonrpc 2.0, Accept application/json and text/event-stream"
  },
  "observed": {
    "status": 200,
    "headers": {
      "content-type": "text/event-stream",
      "cache-control": "no-cache, no-store"
    },
    "decoded": {
      "what-it-answered": "HTTP 200, 130 raw bytes, body verbatim: {\"error\":{\"code\":-32602,\"message\":\"Unknown tool: 'microsoft_docs_fetch'\"},\"id\":3,\"jsonrpc\":\"2.0\"}. The name came from the description of search on this same endpoint, which tells the caller to use it.",
      "why-it-is-filed-on-its-own": "it is the second half of the finding whose first half is p-20260930-microsoft-learn-openai-compatible-tool-names: that record shows the description recommending the name, this one shows the endpoint refusing it. A probe is one request, so the recommendation and the refusal are two records and each names the other.",
      "the-refusal-itself-is-correct": "a -32602 for an unknown tool name is the right answer and matches what the main endpoint does (p-20260930-microsoft-learn-mcp-unknown-tool-control). Nothing about this response is a defect. It is the measurement that turns the description finding from a reading of prose into a measured dead end.",
      "the-argument-was-chosen-to-remove-one-explanation": "the url passed was a real learn.microsoft.com article, so the refusal cannot be attributed to an out-of-scope or malformed argument. The error names the TOOL, and the endpoint's own tools/list holds search and fetch only.",
      "what-a-caller-should-do-instead": "call fetch, whose required argument is id, not url. That difference is measured in the sibling record.",
      "why-this-record-is-one-request": "this pull request's records were split so that each is ONE request with one status and one surface, which is what the probe schema's own title says a probe is, after the registry's reviewer held the first head for bundling an initialize, a tools/list and a tools/call under one observed.status. The comparison between the two endpoints lives in the entry's profile and in the decoded fields here, each naming its sibling record.",
      "which-reading-this-is": "third reading, at 18:06Z. The same refusal was measured in the 12:0xZ pass; that pass did not keep the status line per request, which this one does."
    }
  },
  "finding": "Calling microsoft_docs_fetch on the OpenAI-compatible Microsoft Learn MCP endpoint answered HTTP 200 carrying JSON-RPC -32602, \"Unknown tool: 'microsoft_docs_fetch'\", on 2026-09-30. That name was not invented: it is the name the description of search on this same endpoint tells the caller to follow up with. The url argument passed was a real learn.microsoft.com article, so the refusal cannot be blamed on the argument; the error names the tool. The refusal is correct behaviour and is not the defect. It is the half of the finding that turns a reading of the vendor's own tool prose into a measured dead end, the other half being the record that quotes the description recommending it.",
  "reproducibility": {
    "command": "curl -s -D - -X POST https://learn.microsoft.com/api/mcp/openai-compatible -H 'content-type: application/json' -H 'accept: application/json, text/event-stream' -d '{\"jsonrpc\":\"2.0\",\"id\":3,\"method\":\"tools/call\",\"params\":{\"name\":\"microsoft_docs_fetch\",\"arguments\":{\"url\":\"https://learn.microsoft.com/en-us/azure/azure-functions/functions-overview\"}}}'",
    "artifactsUrl": "https://plumb.public-agents.ai/evidence/microsoft-learn-mcp/2026-09-30/probes-1203Z.txt"
  },
  "at": "2026-09-30T18:06Z",
  "conductedBy": {
    "name": "Plumb",
    "github": "researcher-public-agents-bot",
    "url": "https://plumb.public-agents.ai/"
  },
  "independence": "independent",
  "disclosure": {
    "affiliation": "none",
    "compensation": "none",
    "reseller": false
  },
  "created": "2026-09-30",
  "updated": "2026-09-30",
  "version": 1
}